Semiconductor device and method for making same

ABSTRACT

One or more embodiments relate to a semiconductor device that includes: a conductive layer including a sidewall; a conductive capping layer disposed over the conductive layer and laterally extending beyond the sidewall of the conductive layer by a lateral overhang; and a conductive via in electrical contact with the conductive capping layer.

TECHNICAL FIELD

The present invention relates to semiconductor devices and methods formaking semiconductor devices.

BACKGROUND

In modern integrated circuits, conductive lines may be arranged withindielectric layers to interconnect semiconductor devices. Theseconductive lines may be formed of metal and may be arranged, forexample, on different metallization levels. The conductive lines may besurrounded by, as well as separated by, interlevel dielectric (ILD)layers. Conductive vias can be formed between the conductive lines inorder to provide a conductive connection between different metallizationlevels.

SUMMARY OF THE INVENTION

One or more embodiments relate to a semiconductor device, comprising: aconductive layer comprising a sidewall; a conductive capping layerdisposed over the conductive layer and laterally extending beyond thesidewall of the conductive layer by a lateral overhang; and a conductivevia in electrical contact with the capping layer. In one or moreembodiments, the conductive layer may comprise a metallic material. Inone or more embodiments, the metallic material may comprise a pure metaland/or a metal alloy.

One or more embodiments relate to a semiconductor device, comprising: aconductive layer comprising a sidewall; a conductive capping layerdisposed over the conductive layer and laterally extending beyond thesidewall of the conductive layer by a lateral overhang greater than 2%of the lateral width of the conductive layer; and a conductive via inelectrical contact with the conductive capping layer.

One or more embodiments relate to a semiconductor device comprising: aconductive layer comprising a sidewall; a conductive capping layerdisposed over the conductive layer and extending laterally beyond thesidewall of the conductive layer by a lateral overhang; and a conductivevia disposed over the conductive capping layer and including a portiondisposed lateral to the sidewall of the conductive layer, the portion ofthe via being spaced apart from the sidewall.

One or more embodiments relate to a semiconductor device comprising: ametallic layer comprising a sidewall; a passivation layer disposed onthe sidewall of the metallic layer; a conductive capping layer disposedover the metallic layer; and a conductive via disposed over the cappinglayer and including a portion disposed on the passivation layer.

One or more embodiments related to a method for manufacturing asemiconductor device, comprising: forming a first conductive layer witha sidewall; forming a second conductive layer over the first conductivelayer such that the second conductive layer has an overhang extendinglaterally beyond the sidewall of the first conductive layer; and forminga third conductive layer over the second conductive layer, the thirdconductive layer including a portion formed to the side of the firstconductive layer, a dielectric material being between the portion of thethird conductive layer and the sidewall, the dielectric material beingpart of an interlevel dielectric layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be explained in the followingwith reference to the accompanying drawings, in which:

FIG. 1 shows a conductive via ending on a conductive capping layeraccording to an embodiment of the present invention;

FIG. 2 shows a misaligned conductive via;

FIGS. 3 a-3 c show a comparison between aligned and misalignedconventional conductive vias;

FIGS. 4 a-4 e show a process flow for forming a conductive layer with aconductive capping layer according to an embodiment;

FIG. 5 shows an overhang provided by the conductive capping layer andenhanced sidewall passivation of the conductive layer;

FIG. 6 shows a failure distribution for a conductive via using theconductive capping layer according to embodiments of the presentinvention; and

FIG. 7 shows a conductive via ending on a conductive capping layeraccording to an embodiment of the present invention.

Before embodiments of the present invention will be explained in moredetail in the following on the basis of the drawings, it is pointed outthat like elements in the figures are provided with the same or similarreference numerals, and that a repeated description of these elements isomitted.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In modern integrated circuits conductive layers between semiconductordevices are often formed as metal layers or lines arranged withindielectric layers. These metal layers or lines can, for example, bearranged on different metallization levels and can be separated byinterlevel dielectric layers (ILD). The interlevel dielectric layers maycomprise any dielectric material. Examples include oxides, nitrides,oxynitrides or combinations thereof

In one or more embodiments, the metal layers or lines may comprise anymetallic material. The metal layers or lines may comprise pure metalsand/or metal alloys. Conductive via interconnections or simplyconductive vias can be formed in order to provide a conductiveconnection between different interconnections or metal lines. For areliable connection it is important that the conductive vias land on themetal lines and no short circuits appear and, hence, a reliablemisaligned or borderless via interconnect is formed. In one or moreembodiments, the conductive vias may comprise any metallic material. Themetallic material may comprise a pure metal and/or a metal alloy.

In back end of line (e.g., BEOL) technology a wiring concept of metallines may comprise, for example, Al (the element aluminum) and/or Cu(the element copper). Hence, the metal lines may comprise, for example,one or more of the materials selected from the group consisting ofaluminum metal and copper metal. The aluminum metal may comprise purealuminum and/or aluminum alloy. The aluminum alloy may, for example, bean aluminum-copper alloy. The copper metal may comprise pure copperand/or copper alloy. The copper alloy, may for example, be acopper-aluminum alloy. In one or more embodiments, the metal lines may,for example, be formed as a first metal/second metal stack where thefirst metal/second metal may be aluminum metal/copper metal or it may becopper metal/aluminum metal.

A capping layer may be formed over the metal lines. The capping layermay comprise, for example, a titanium metal/titanium nitride (Ti/TiN)stack or tantalum metal/tantalum nitride (Ta/TaN) stack. The titaniummetal may comprise pure titanium and/or titanium alloy. The tantalummetal may comprise pure tantalum and/or tantalum alloy.

A conductive via may then be formed over the capping layer andelectrically contact the capping layer. In one or more embodiments, theconductive via may actually physically contact the capping layer. Theconductive via may stop in the capping layer. The conductive via maycomprise a tungsten metal. The tungsten metal may comprise pure tungstenand/or tungsten alloy.

In one or more embodiments, a capping layer may include a TiN or TaNfilm which may promote tungsten metal fill nucleation. The capping layermay provide no containment to the precursors used for the tungsten metalfill and a problem may emerge if the conductive via touches orperforates a sidewall of the metal line due to a lateral overlay errorwith respect to the underlying metal line. This problem may be avoidedif the metal line comprises a sufficient overhang with respect to theconductive via and the metal line, wherein the amount of overhang isgiven by the manufacturing tolerances or the manufacturing errors.

On the other hand, in order to minimize chip area, conventional BEOLtechnology is often designed with zero via/line overlap or with acorresponding marginal overlay specification, which is less than thetypical tolerances and variances of the processes and the integrationscheme. The consequence is that conductive vias are often not fullylanded over the metal line, but the via hole etch extends deeply intothe interlevel dielectric (ILD) layer laterally next to the line. In anextreme case, this leads to increased intra- or interlevel leakage oreven shorts. But even if such interlevel shorts can be avoided, the viahole etch, subsequent via hole clean and the tungsten metal via fillprocess can comprise detrimental impact on the sidewall of the metalline, which is hit by these processes. Especially a via hole fillprocess as, for example, using tungsten-hexafluoride (WF6) precursorsmay be very aggressive with respect to a metal line.

If the conductive via does not reliably stop in the capping layer due toa direct breakthrough, or if the conductive via touches or perforatesthe metal line sidewall (due to the lateral overlay error with respectto the underlying metal line), the via hole etch process and/or the viahole clean process and/or the liner fill process may take place on themetal line surface (e.g., along the sidewall) leading to a number ofmechanisms hampering the via/metal interface. In addition, the tungstenmetal fill process may no longer be contained by the capping layer andmay affect the conductive via/capping layer/metal line interface,and/or, attack the exemplary aluminum metal or copper metal material ofthe metal line.

Depending on the precursors used for the tungsten fill, for example, ahigh ohmic AlF (Aluminum Fluoride) interface, or a void between an AlCualloy and tungsten metal via, will be the result. This can cause a shiftin the resistance of the conductive via/metal line interface andprovides a mechanism for electro migration failure and thus a reductionof the operation time to failure. Therefore, it is important to ensurethat the metal line remains shielded during the process of forming theconductive via. In fact, the electro migration lifetime of misalignedconductive via/line interconnects is significantly worse than awell-processed reference.

To avoid the above-mentioned mechanism, the conductive via, while partlymisaligned with respect to the underlying metal line, should notperforate the metal line (which may, for example, be an AlCu alloy).

Conventional approaches either try to avoid the conductive via/linemisalignment by:

-   -   (i) providing landing pads covering the expected overlay error;        or    -   (ii) limiting the tolerable overlay error.

In these approaches either the routing pitch and hence the chip size isconsiderably increased or the overlay-rework is increased. In addition,more performance and/or more expensive lithographic tools may be needed.In other conventional approaches the misalignment is allowed, but thedetrimental attack of the metal line is avoided by either using one ormore etch stop/hard mask layer, by applying additional spacers next tothe metal line sidewalls. These conventional approaches consume chiparea, increase processing costs and complexity and do not provide areliable overall protection. Especially in aggressive design rules,there is a latent risk that conductive vias might (occasionally) bemisaligned and that the conductive via/metal line reliability might nolonger meet the requirements.

Hence, there is a need for a solution, which allows borderless or evenmisaligned conductive vias without sacrificing the liability performanceor increasing process complexity and costs.

Embodiments of the present invention accomplish this by making use of adeliberate overhang of the conductive line with a conductive cappinglayer having an overhang with respect to the underlying metal line and,optionally, a deliberately enhanced passivation of the sidewall of themetal line. The passivation layer may, for example, comprise an oxideand/or a nitride. In one or more embodiments, the passivation layer maybe used with the overhang. In one or more embodiments, the passivationlayer may be used without the overhang. In one or more embodiments, theconductive via may contact the passivation layer.

Therefore, embodiments of the present invention relate to asemiconductor device comprising a conductive layer (for example, a metallayer or metal line) comprising a sidewall (for example, a lateralsidewall), a conductive capping layer disposed over the conductive layerand laterally extending beyond the sidewall (for example, the lateralsidewall) of the conductive layer by an overhang. In one or moreembodiments, the overhang may be greater than about 5 nm. In one or moreembodiments, the overhang may be greater than about 10 nm. In one ormore embodiments, the overhang may be greater than about 15 nm. In oneor more embodiments, the overhang may be greater than about 20 nm. Inone or more embodiments, the overhang may be less than about 50 nm. Inone or more embodiments, the overhang may be less than about 40 nm. Inone or more embodiments, the overhang may be between about 5 nm andabout 50 nm.

The semiconductor device further comprises a conductive via. Theconductive via may be formed over the conductive capping layer and maybe in electrical contact with the conductive capping layer. In one ormore embodiment, the conductive via may be in contact with theconductive capping layer. One or more dielectric layers, such as one ormore interlevel dielectric (ILD) layers may be laterally surrounding theconductive layer, the conductive capping layer and the conductive via.

Embodiments of the present invention also comprise a method formanufacturing a semiconductor device, wherein the method comprisesforming a conductive layer, forming a conductive capping layer over theconductive layer so that the conductive layer extends beyond thesidewall of the conductive layer by a lateral overhang. In one or moreembodiments, the lateral overhang may extend over about 5 nm. The methodcomprises optionally structuring or patterning of the conductive layerand the conductive capping layer. The step of structuring comprises, forexample, an annealing process and/or a selective wet-chemical etchingprocess and/or a dry etching process. In one or more embodiments, thedry etching process may comprise metal reactive ion etching (RIE).Optionally, the method comprises a passivation step after the dry (forexample, RIE) etching or a wet-chemical step. Optionally, the methodcomprises an annealing step after the RIE metal etching.

Embodiments thus provide an overhang of the conductive capping layerwith respect to the metal line and may, optionally, comprise an enhancedsidewall passivation of the metal line.

By making use of an intentionally pronounced overhang of the cappinglayer with respect to the underlying metal line and/or optionally by adeliberately enhanced passivation of the line sidewall a partlymisaligned via may not yield to an attack of the line during theprocessing. As a result, embodiments of the invention tolerateborderless or misaligned conductive vias and prevent any detrimentalattack to the metal line. This may be accomplished by either leaving anarrow interlevel dielectric layer or volume between the conductive viaand the metal line and/or by providing a deliberate sidewallpassivation. The sidewall passivation may, for example, provide an oxideor a nitride surface of the metal line. Embodiments show uniqueelectrical and reliability performance without increasing process costs,complexity or chip size.

Thus, embodiments allow borderless and/or misaligned vias by avoidingany detrimental attack of the metal line by leaving a distinct volume ofthe intermetal dielectric layer (e.g., the ILD layer) and/or optionallyanother type of protective layer between a sidewall of the metal lineand a portion of the conductive via which is laterally spaced apart fromthe sidewall. A detrimental attack of the metal line can, for example,be caused by the via etch, the cleaning or the WF6 (tungstenhexafluoride)-chemistry, and other processes. Thus, the metal linesidewall is no longer exposed to any attack at any state of processingeven in the case of a partly misaligned via.

Further benefits of embodiments comprise structures with misaligned viasthat show identical reliability performance, for example, with respectto electromigration and stress migration, and identical electricalparameters as those with fully landed vias. Embodiments do not requireor need a separate landing pad and hence less chip area is consumed. Inaddition, overlay specification can be relaxed and even borderless viasare tolerated. Further benefits comprise that less-(overlay) performancetools can be used for exposure and less rework is required (no expensivephotolithographic tools are needed). Since no extra layers or processesare needed also low costs and low complexity can be maintained and astandard PVD-liner (physical vapour deposition) can be used for tungstenfill.

FIG. 1 shows a semiconductor device according to an embodiment of thepresent invention, wherein a conductive layer 110 comprising a sidewall112 (for example, a lateral sidewall), and wherein a conductive cappinglayer 120 is arranged over the conductive layer 110 and laterallyextends beyond the lateral sidewall 112 of the conductive layer 110 bythe lateral overhang D. In one or more embodiments, the lateral overhangD may greater than about 5 nm. In one or more embodiments, the overhangD may be greater than about 10 nm. In one or more embodiments, theoverhang D may be greater than about 15 nm. In one or more embodiments,the overhang D may be greater than about 20 nm. In one or moreembodiments, the overhang D may be less than about 50 nm. In one or moreembodiments, the overhang D may be less than about 40 nm.

In the embodiment shown in FIG. 1, the semiconductor device comprises aconductive via 130 disposed over the capping layer 120 and in electricalcontact with the capping layer 120. In the embodiment shown, theconductive via 130 is disposed on the capping layer 120, however, inother embodiments, it is possible that one or more additional layers bedisposed between the conductive via 130 and the capping layer 120. Thedevice may further comprise a dielectric layer 140 which laterallysurrounds the conductive layer 110 and the conductive capping layer 120as well as the conductive via 130. The dielectric layer 140 may compriseone or more interlevel dielectric (ILD) layers.

Possible materials for the layers can be chosen such that conductivelayer 110 may comprise any conductive material. In one or moreembodiments, the conductive material may comprise any metallic material.In one or more embodiments, the conductive material may comprise atleast one of the elements Al or Cu. In one or more embodiments, theconductive layer 110 (which may, for example, be a metal layer or metalline) may comprise, for example, aluminum metal and/or copper metal, theconductive capping layer 120 comprises, for example, titanium metaland/or titanium nitride and the conductive via 130 comprises, forexample, tungsten metal. The titanium metal may be pure titanium or atitanium alloy. The tungsten metal may be pure tungsten or tungstenalloy. The aluminum metal may be pure aluminum or aluminum alloy. Thecopper metal may be pure copper or a copper alloy. In one or moreembodiments, the conductive layer may be an aluminum alloy.

The conductive capping layer 120 may serve, for example, as ananti-reflective coating (ARC) during lithographic processes, as a stressrelease between the material of the conductive via 130 and theconductive layer 110 and, in addition, can be used as a etch stop layerin the process of forming an opening for the conductive via 130 withinthe dielectric layer 140. The dielectric layer 140 can, for example, beone of the interlevel dielectric (ILD) layers or intermetal dielectriclayers within an integrated circuit. In one or more embodiments, thecapping layer 120 may comprise a conductive nitride. Examples includeTiN and TaN. In one or more embodiments, the capping layer 120 may be astack such as a titanium metal/TiN stack or a tantalum metal/TaN stack.

FIG. 2 shows a partially misaligned conductive via 130 disposed over thecapping layer 120. The conductive via 130 is misaligned with respect toa capping layer 120 by a misalignment M. In the embodiment as shown inFIG. 2, the misalignment M appears with respect to the left-hand side ofthe conductive capping layer 120. As a result, when forming an openingfor the conductive via 130 within the dielectric layer 140, the openingcontinues on the left-hand side of the capping layer 120 up to a depth Lbeneath the conductive capping layer 120. As a result, the conductivevia 130 includes a portion which directly overlies the capping layer 120as well as a portion 130P which is disposed lateral to the conductivelayer 110 and spaced apart from the sidewall 112 of the conductive layer110. Hence, because the capping layer 120 extends laterally beyond thesidewall 112, conductive via 130 includes a portion 130P which islaterally disposed from and also spaced apart from the sidewall 112. Theportion 130P is laterally separated from the sidewall 112 by a portionof the dielectric layer 140 within a region R. The portion of thedielectric layer 140 within the region R may also be part of aninterlevel dielectric (ILD) layer.

The portion of the dielectric layer 140 within the region R may comprisea thickness of approximately the lateral overhang D of the conductivecapping layer 120 over the conductive layer 110 and reflects theaforementioned overhang effect of the conductive capping layer 120 withrespect to the conductive layer 110. In addition, the overhang D can bechosen such that the portion of the dielectric layer 140 within theregion R is strong enough to withstand the processing (e.g., the usedaggressive chemistry) of the conductive via 130.

In the embodiment as shown in FIG. 2 between the conductive cappinglayer 120 and the conductive layer 110 an optional intermediate layer125 may be disposed, which can, for example, be used as a further stressrelease between the conductive capping layer 120 and the conductivelayer 110.

In one or more embodiments, as a further option, the conductive layer110 can comprise a passivation layer 116, which may be formed along thesidewall 112 of the conductive layer 110. The passivation layer 116 mayserve as additional protection with respect to processes of forming theconductive via 130.

The optional passivation layer 116 may, for example, comprise an oxideor a nitride. The oxide may, for example, be aluminum oxide which may beformed by an oxidation process, which is done, for example, afterforming the conductive layer 110.

In one or more embodiments, a base layer 118 may be formed below theconductive layer 110. The base layer 118 may comprise, for example,titanium metal and/or titanium nitride (TiN).

In one or more embodiments, the conductive capping layer 120 comprises athickness B1, which may be, for example, within a range of about 10 nmto about 80 nm or between about 30 nm and about 60 nm or between about40 nm and about 45 nm.

In one or more embodiments, the lateral overhang D of the conductivecapping layer 120 may be within the range of about 5 nm and about 50 nm.The overhang D may be measured with respect to the sidewall 112 of theconductive layer 110. Examples include, but are not limited to, overhangdistances of about 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, and 40 nm.In one or more embodiments, the overhang D may be greater than about 2%of a lateral width W of the conductive layer 110. In an embodiment, theoverhang D may be at least about 5% of a lateral width W of theconductive layer 110. In an embodiment, the overhang D may be at leastabout 10% of a lateral width W of the conductive capping layer 120. Inan embodiment the overhang D may be less than about 20% of the lateralwidth of the conductive layer 110. In an embodiment, the overhang D maybe less than about 15% of the lateral width of the conductive layer 110.

An optional intermediate layer 125 may be disposed between the cappinglayer 120 and the conductive via 130. The intermediate layer may beformed of a conductive material. In one or more embodiments, theintermediate layer may be metallic. In one or more embodiments, theintermediate layer may be a conductive nitride. The intermediate layer125 comprises a thickness B2, which is, for example, within a range ofabout 2 nm to about 12 nm or between about 2 nm and about 7 nm orbetween about 3 nm to about 6 nm or about 5 nm.

The conductive layer 110 comprises a thickness B3, which is, e.g.,within a range between about 200 nm and about 1000 nm or between about200 nm and about 500 nm or between about 250 nm and about 500 nm orbetween about 300 nm and about 350 nm or about 330 nm. In one or moreembodiments, the conductive layer 110 may be a metal layer such as ametal line. In one or more embodiments, the conductive layer 110 maycomprise a metallic material. In one or more embodiments, the conductivelayer 110 may comprise the element Al and/or the element Cu. Theconductive layer 110 may comprise an AlCu alloy comprising, Al withabout a portion of Cu (the element copper) within a range of about 0.2%to about 1% or about 0.5%. In one or more embodiments, the conductivelayer 110 may comprise at least one material selected from the groupconsisting of pure aluminum, aluminum alloy, pure copper, and copperalloy.

In further embodiments the capping layer 120 comprises a layer stack offurther layers, with materials such that a further stress release isachieved or the electromigration or stress migration is further limited.Perpendicular to the drawing plane, the conductive layer 110 may extendbeyond the conductive via 130, which may contact the conductive layer110 only within a contact region. In further embodiments, the conductivevia 130 forms a conductive interconnect so that the conductive via 130electrically contacts to conductive layers on both ends, which meansthat in FIG. 2 only one conductive layer is shown and the conductive via130 extends up to a next level, in which a further conductive layer isarranged (towards the top of the drawing plane in FIG. 2, not shown inFIG. 2).

FIGS. 3 a to 3 c show a conventional device with a conductive via 230 aending on a conventional capping layer 220.

FIG. 3 a shows manufacturing variations for a processed device, forexample at different places on a wafer. In detail, two figures, one onthe left and one on the right hand side, are shown on the top, in whichthe conductive vias 230 a, 230 a′ slightly vary with respect to theirlateral alignment. Each top figure comprising a first conventionalconductive layer 210 a, 210 a′ and a second conventional conductivelayer 210 b, 210 b′, wherein the first conductive layers 210 a, 210 a′comprise first capping layers 220 a, 220 a′ and the second conductivelayers 210 b, 210 b′ comprises a second conductive capping layer 220 b,220 b′. The first conductive layers 210 a, 210 a′ are contacted with theconventional conductive vias 230 a, 230 a′, which are both partiallymisaligned by the misalignment M (for the first conductive via 230 a onthe left hand side of the top figures) or by the misalignment M′ (forthe first conductive via 230 a′ on the right hand side of the topfigures). As result in both cases the conductive vias 230 a, 230 a′extend along the sidewalls 212 a, 212 a′ of the conductive layers 210 a,210 a′.

On the bottom of FIG. 3 a magnified pictures of the top figures areshown, which show more details of the conductive vias 230 a, 230 a′ andthe capping layers 220 a, 220 a′. For these conventional capping layers220 no protection is provided for the conductive layers 210 which arethus in direct contact with the conductive vias 230. Hence, inprocessing the conductive vias 230, which use often aggressivechemistry, a damaging of the conductive layer 210 or an optionalintermediate layer can in principle not be excluded. The lateralmisalignments M, M′ comprise, for example, a value within a rangebetween about 50 and about 80 nm.

FIG. 3 b shows in contrast to FIG. 3A an aligned conductive via 230 cwith the conductive layer 210 a. This is the ideal situation, which ingeneral cannot be ensured, or only with an increase in the manufacturingcomplexity and costs. Misaligned vias can be avoided only if a safetymargin E of the conductive via 230 c to the edge of the conductivecapping layer 220 a is bigger than the manufacturing variations in themisalignment M.

FIG. 3 c shows a diagram of a failure distribution N with two examples Aand B of misaligned conductive vias and two examples C and D of alignedvias. This distribution comprises the statistic obtained frommanufacturing a device, for example, at different places on a wafer oron different wafers. The failure distribution as shown in FIG. 3 c givesa percentage as a function of time t measured in hours of operation, forexample, when a failure occurs. The distributions N are normalized suchthat N=0 corresponds to about a 50% failure rate. The misalignedexamples A and B group together along the lines 310 a and 310 b, whereasthe aligned example C and D are grouped together along the lines 310 cand 310 d. From this diagram it is clear that the aligned examples C andD comprise a significant improvement in the failure rate, which meansthe failure occurs at later times.

FIGS. 4 a to 4 e show a possible process flow for forming a conductivelayer 110 with a conductive capping layer 120 according to embodimentsof the present invention.

FIG. 4 a shows a first step, wherein on a substrate 410 the conductivelayer 110 and the conductive capping layer 120 are formed such that theconductive layer 110 is arranged between the conductive capping layer120 and the substrate 410. Optionally between the substrate 410 and theconductive layer 110 further conductive or dielectric layers can beformed.

FIG. 4 b shows as a next step a structuring or patterning, which can,for example, be performed by using a (hard) mask layer 420, which isformed on the conductive capping layer 120. The mask layer 420 definesthe position or the region the conductive layer 110 shall be formedwithin.

FIG. 4 c shows the next step in which, for example, an etching isperformed such that the conductive capping layer 120 and the conductivelayer 110 are removed outside the region, which was defined by the hardmask layer 420. The etching can, for example, comprise multiple etchingsteps, which are selective with respect to the material used for theconductive capping layer 120 and another etching can be selective withrespect to the material for the conductive layer 110. The substrate 410acts as a stop layer for this etching process. Embodiments used for theetching process have different selectivities for the materials of thecapping layer 120 and the conductive layer 110, so that the conductivelayer 110 is laterally recessed in a direction towards the sidewall 112of the conductive layer 110 (or in a direction anti-parallel to a normalvector of the sidewall 112). Due to this recess, the conductive cappinglayer 120 extends laterally beyond the sidewalls 112 of the conductivelayer 110. In one or more embodiments, the conductive layer 110 may beetched at a faster rate than the capping layer 120.

FIG. 4 d shows the next step in which the dielectric layer 140 is formedon the substrate 410 and the remaining hard mask layer 420.

Finally, FIG. 4 e shows how the dielectric layer 140 is opened andfilled with conductive material so that the conductive via 130 contactsthe conductive capping layer 120. The process of opening the dielectriclayer 140 can, for example, comprise an etching step, which is selectivewith respect to the material of the dielectric layer 140 as well as withrespect to the material of the mask layer 420. As a result, the masklayer 420 is removed on the conductive capping layer 120 and theconductive via 130 gets in direct contact with the conductive cappinglayer 120. A remaining part of the hard mask layer 430 can remainlaterally next to the conductive via 130, which was not opened by thissecond etching step. This opening may comprise an overlay error M sothat the lateral position of the conductive via 130 may vary withinmanufacturing variations and as consequence the conductive via 130 mayextend also laterally next to the conductive capping layer 120 up to adepth L underneath a surface of the conductive capping layer 120.

This processing yields a conductive capping layer 120 which may be usedto avoid the attack of the sidewall 112 of the conductive layer 110,because the misaligned via is separated from the conductive layer 110still by a portion of the IMD dielectric layer 140 within the region Rbetween the conductive layer 110 and the conductive via 130.

The overhang of the capping layer 120 with respect to the conductivelayer 110 below can be accomplished by several further techniques or bycombining several mechanisms. One example comprises an annealing steppost the metal etch as shown in FIG. 4 c, which leads to the lateralrecess of the conductive layer 110 with respect to the conductivecapping layer 120 over the whole sidewall 112. This annealing step canalso be modified in a way that it makes additional use of a formation ofaluminum titanate in the upper or lower part of the conductive layer110. This aluminum titanate occurs, for example, since the conductivelayer can comprise the element Al (for example, it may comprise aluminummetal) and the conductive capping layer 120 or the optional intermediatelayer 125 comprise the element titanium (for example, it may comprisetitanium metal such as pure titanium or titanium alloy) and bothmaterials can react within the annealing step.

The forming of the aluminum titanate may result in a reduction of thevolume since aluminum titanate may comprise a smaller volume thantitanium metal itself. This process can, for example, be controlled bythe amount of the element titanium added.

A further possibility for accomplishing the overhang of the conductivecapping layer 120 may comprise, for example, a selective wet-etchingstep post the metal etch, wherein the selective wet-chemical etchingremoves material from the conductive layer 110, but less material fromthe conductive capping layer 120. The metal etch step comprises, forexample, a reactive ion etching (RIE) and as explained at FIG. 4 c thisreactive ion etching can also be used for directly developing the roofof the conductive capping layer 120 due to its lower lateral etch rateof the conductive capping layer 120 compared to the material of theconductive layer 110.

Optionally between the steps as shown in FIG. 4 c and 4 d, further stepscan be performed in order to generate the enhanced passivation layer 116along the sidewalls 112 of the conductive layer 110. This enhancedsidewall passivation can also be used to avoid the attack of thesidewall 112 of the conductive layer by the processing of the misalignedvia. The following steps can, for example, accomplish this passivationenhancement. One possibility is a passivation step post the RIE etching,which was used, for example, to form the structure as shown in FIG. 4 c.This passivation step can, for example, comprise an oxidation, a plasmaoxidation or a nitration. A further possibility to achieve thepassivation comprises a wet-chemical passivation step, which can, forexample, comprise a DSP clean (DSP=double side polishing). Finally anoptional annealing step post the metal etching step can also generatethe passivation layer 116.

FIG. 5 shows a misaligned via, wherein the conductive via 130 extendsdue to the overlay error M up to a depth L beneath the conductivecapping layer 120. Due to the overhang of the conductive capping layer120 there is still a barrier within the region R between the conductivevia 130 and the conductive layer 110. The dielectric layer 140 cancomprise, for example, an ILD oxide. In addition, the conductive layer110 comprises the optional passivation layer 116 which provides anadditional passivation barrier between the conductive via 130 and theconductive layer 110. FIG. 5 shows also the remaining part 430 of thehard mask layer, which was left over after the opening of the dielectriclayer 140 as shown in FIG. 4 e. The conductive via 130 contacts theconductive capping layer 120 over a contact region C1 comprising adiameter within a range of, for example, around 100 nm to 150 nm or ofaround 124 nm. Due to the overlay error M the conductive via 130 doesnot contact the conductive layer 110 within a region C2, which may, forexample, comprise a value between 50 nm and 100 nm or of about 82 nm.The overlay error M can comprises, for example, a value within a rangeof about 10 nm to about 100 nm or of about 55 nm. The remaining part ofthe hard mask layer 430 can, for example, comprise silicon-oxy-nitride(SON).

The embodiment as shown in FIG. 5 comprises therefore both features, thefirst feature of overhang of the conductive capping layer 120 withrespect to the conductive layer 110 and the second feature of theenhanced sidewall passivation 116, which is formed along the sidewall112 of the conductive layer 110. The conductive layer 110 can, forexample, be patterned by using a silicon-oxy-nitride hard mask.

FIG. 6 shows a further failure distribution, but now using a conductivecapping layer 120 according to embodiments. Again a percentage offailure of conductive vias as a function of the time (as measured inhours of operation) is shown. In one example the conductive via isaligned, a first example A comprises misaligned conductive vias withrespect to, for example, about 10 nm in one direction and a secondexample B corresponds to a misalignment of about 50 nm with respect tothe other direction. The failure times of all three examples show nowcomparable results, so that the misaligned conductive vias show nodetrimental effects with respect to the failure time. Therefore,embodiments of the present invention exhibit reliable misaligned orborderless vias with comparable fail times and same spread a as PORreference.

In order to achieve the benefits of the embodiments a highly selectivevia etch and a sufficient thickness for the conductive capping layer maybe used.

In one or more embodiments, the conductive capping layer may comprise avia hole etch through the interlayer dielectric, which stops selectivelyin the capping layer. In one or more embodiments, the capping layer mayserve as an anti-reflective coating layer. In one or more embodiments,the capping layer may, for example, include TiN or TaN. In one or moreembodiments, the capping layer may include a titanium metal/TiN stackand/or a tantalum metal/TaN stack. A via etch may be performed with astop in the capping layer or with a stop in the remaining hard mask 430combined with a selective hard mask breakthrough. Embodiments of thepresent invention also comprise a modification of the typical metal etch(for example, the RIE etching) so that the etching rate is selectivewith respect to the materials of the conductive layer 110 and theconductive capping layer 120. For example, the selectivity can be chosensuch that more material of the conductive layer 110 is removed thanmaterial of the conductive capping layer 120, which will formautomatically the lateral overhang of the conductive capping layer 120.An optional DSP cleaning can also be included. This etching process canbe adjusted so that the lateral etching rate and hence the desiredoverhang (lateral overhang) of the conductive capping layer 120 over theor beyond the sidewall 112 of the conductive layer 110 is achieved. Theresulting overhang comprises a lateral dimension of the capping layer,which is larger than the dimension of the conductive layer (which, forexample, may be a metal line) itself.

The optional intermediate layer 125 comprises a material, which mayminimize the electromigration between the conductive capping layer 120and the conductive layer 110. In one or more embodiments, theintermediate layer 125 may comprise any conductive material. In one ormore embodiments, the intermediate layer 125 may be a metallic material.In one or more embodiments, the intermediate layer comprises the elementTi. The intermediate layer may comprises titanium metal such as puretitanium and/or titanium alloy. In an embodiment, the intermediate layermay comprise the element tantalum and may comprise tantalum metal (suchas pure tantalum and/or tantalum alloy).

A further aspect is that also the stress migration should be minimized.Hence, embodiments show identical electro migration and/or stressmigration and electrical parameters as non-misaligned test structures.

The ideas described above are also applicable to damascene processes(for example, single or dual damascene processes). The damasceneprocessing may be particularly useful in applications based upon acopper metal line technology. Another embodiment of the invention isshown in FIG. 7. FIG. 7 shows a lower metal layer 510, a capping layer520, a metal via 530 and an upper metal layer 540. FIG. 7 also shows adielectric material 550.

The upper metal layer 540 and the via 530 may be formed using adamascene process. Openings may first be formed in the dielectricmaterial 550. A seed layer may then be formed on the surfaces of theopenings and a metallic material may then be electroplated onto the seedlayer. In one or more embodiments, the lower metal line 510, upper metalline 540 as well as the conductive via 530 may comprise any metallicmaterial. In one or more embodiments, the metallic material may includethe elements Cu and Al. In one or more embodiments, the metallicmaterial may comprise copper metal and/or aluminum metal. The coppermetal may be pure copper or copper ally. The aluminum metal may bealuminum metal or aluminum alloy.

The openings 532 and 542 may, for example, be formed by a dual damasceneprocess. A capping layer 520 is formed over the lower metal line 510.The capping layer 520 is formed so as to have an overhang D. The cappinglayer 520 may comprise any of the materials described above for thecapping layer. An intermediate layer may be disposed between the cappinglayer 520 and the metal line 510. The conductive via 530 is disposedover the metal line 510.

In the embodiment shown, the conductive via is misaligned such that aportion 535 of the conductive via 530 extends below the top surface ofthe lower metal layer 510. The portion 535 is spacedly disposed from asidewall surface of the lower layer 510 by a portion of the dielectricmaterial 550.

Features of embodiments of the present invention can easily be combinedwith any other features, process or method, in order to optimize thebenefits under certain aspects.

What is claimed is:
 1. A semiconductor device comprising: a conductivelayer comprising a sidewall; a conductive capping layer disposed overthe conductive layer and extending laterally beyond the sidewall of theconductive layer by a lateral overhang; and a conductive via disposedover the conductive capping layer, wherein a portion of the conductivecapping layer is arranged between the conductive layer and theconductive via, and wherein the conductive via includes a portionextending past the conductive capping layer and laterally facing butspaced from the sidewall of the conductive layer by a distance.
 2. Thedevice of claim 1, further comprising a dielectric material disposedbetween the portion of the via and the sidewall, the dielectric materialbeing part of an interlevel dielectric layer.
 3. The device of claim 1,further comprising an intermediate layer disposed between the conductivecapping layer and the conductive layer.
 4. The device of claim 1,further comprising a passivation layer along the sidewall of theconductive layer.
 5. The device of claim 1, wherein the conductive layercomprises a metallic material.
 6. A semiconductor device comprising: aconductive layer comprising a sidewall; a conductive capping layerdisposed over the conductive layer and extending laterally beyond thesidewall of the conductive layer by a lateral overhang; a conductive viain electrical contact with the conductive capping layer, wherein aportion of the conductive capping layer is arranged between theconductive layer and the conductive via, and wherein the conductive viaincludes a portion extending past the conductive capping layer andlaterally facing but spaced from the sidewall of the conductive layer bya distance; and a dielectric material between the portion of the via andthe sidewall, the dielectric material being part of an interleveldielectric layer.
 7. The device of claim 6, further comprising apassivation layer along the sidewall of the conductive layer.
 8. Thedevice of claim 6, wherein the conductive layer comprises a metallicmaterial.
 9. The device of claim 6, wherein the conductive via is indirect contact with the capping layer.
 10. A semiconductor devicecomprising: a metallic layer comprising a sidewall and formed in adielectric layer; a passivation layer disposed on the sidewall of themetallic layer between the metallic layer and the dielectric layer; aconductive capping layer disposed over the metallic layer; and aconductive via disposed over the capping layer and including a portiondisposed on the passivation layer.
 11. The device of claim 10, whereinthe passivation layer comprises an oxide or a nitride.
 12. The device ofclaim 10, wherein the passivation layer comprises aluminum oxide. 13.The device of claim 10, wherein a portion of the conductive cappinglayer is arranged between the metallic layer and the conductive via.